1. Institute of Polymers, Bulgarian Academy of Sciences, 1113 Sofia, Bulgaria
2. Institute of Polymers, Bulgarian Academy of Sciences, 1113 Sofia, Bulgaria,
3. Institute of Molecular Biology, Bulgarian Academy of Sciences, 1113 Sofia, Bulgaria
4. Faculty of Pharmacy, Academy of Medicine, 1000 Sofia, Bulgaria
5. Laboratoire d'Etudes des Métariaux Plastiques et des Biomatériaux URA-CNRS 507, Université Claude Bernard Lyon I, 69622 Villeurbanne Cedax, France